Preparation of chlorine pentafluoride



' Frank C. Gunderloy,

United States Patent 3,363,985 PREPARATION 0F CHLORINE PENTAFLUORIDE Jr., Woodland Hills, Walter Maya, Los Angeles, and Richard D. Wilson, Canoga Park, Califi, assignors to North American Aviation, Inc. No Drawing. Filed Sept. 17, 1963, Ser. No. 310,970 4 Claims. (Cl. 23--205) This invention relates to a process for preparation of chlorine pentafluoride (Cl-F by reaction of fluorine with tetrafluorochlorates of certain alkali metals.

A method for the preparation of ClF by subjecting a mixture of fluorine and chlorine, for example, to a glow discharge is described in patent application, Ser. No. 253,521, filed Jan. 21, 1963, by Walter Maya and Hans P. Bauer. As therein mentioned, ClF is an extremely highenergy oxidizer of greater oxidizing potential than chlorine trifluoride which finds utility as an oxidizer for rocket propellant fuels. The boiling point of ClF is about -14 C.

By the above-mentioned glow discharge process, the yields of ClF are relatively low and various resultants are produced requiring cryogenic fractionation for separation, whereas according to the process of the instant invention only one coudensable gaseous resultant (GR) is produced.

There are three known alkali metal tetrafluorochlorates, they being the potassium, cesium and rubidium species. Lithium and sodium tetroiiuorochlorates are not known to have been produced. The reactions of the process of this invention may be represented by the equation:

EXAMPLE 1 0.1 mole (15.2 g.) of cesium fluoride was placed in a 150 ml. stainless steel bomb and 0.13 mole (3,000 cc.) of

group consisting of chlorine trifluoride was condensed into the bomb with cooling of the bomb in a bath of liquid nitrogen. The bomb was then heated to C. for 4 hours and was then evacuated through a l96 C. trap for collecting the unreacted CIF which was measured and found to be about 0.04 mole. 4,000 cc. of fluorine were then condensed into the bomb and the contents of the bomb was maintained at about 80 C. for six hours, the initial pressure in the bomb being about 520 p.s.i.

The bomb was then immersed in a bath of liquid nitrogen and the excess fluorine was pumped off. The bomb was connected to a train of traps at temperatures not above -112 C., and the liquid nitrogen bath was removed from the bomb. A total of 0.04 gram (.003 mole) of ClF was found in the traps along with traces only of impurities, e.g., FClO and C10 The yield of CIF was calculated to be 0.33 percent on the basis of the amount (0.09 mole) of ClF which reacted with the cesium fluoride, which basis has its equivalent in terms of cesium tetrafluorochlorate initially formed and thereafter fluorinated.

EXAMPLE 2 0.1 mole (5.8 g.) of potassium fluoride was placed in a 150 ml. stainless steel bomb containing small nickel rods and 0.13 mole (3,000 cc.) chlorine trifluoride was condensed into the bomb. The bomb was rotated overnight at room temperature. Thereafter the excess (about 0.08 mole) ClF was removed, showing the KF reacted with the ClFg in a ratio of 1 to .5, thus indicating that the tetrafiuorochlorate was a double salt, represented as 4,000 cc. of fluorine were then condensed into the bomb. The bomb was maintained at about 200 C. for about 27 hours, the initial pressure in the bomb at 200 C. being about 800 p.s.i. A total of 0.39 gram of ClF was recovered and the yield was calculated to be 6 percent.

EXAMPLE 3 The same technique as that described in Example 2 was followed, using rubidium fluoride in the place of potassium fluoride and 5.3 percent yield of ClF was recovered.

EXAMPLES 4-26 The same technique as that described in Example 2 was followed for the examples contained in Tables I and II.

TABLE I.-FLUORINATION OF POTASSIUM TETRAFLUOROCHLORATE Example KClFyKF Fluorine Initial Temp, Time, 011%,

No. in moles in liters Pressure 0. Hours percent in p.s.i. yie

See Notes at end of Table II.

TABLE II.FLUO RINATION OF GESIUM TET RAFLUO R CHLO RATE Example CsGlF Fluorine Initial Temp, Time, ClFs,

No. in moles in liters Pressure 0. Hours percent in p.s.i. yield contents of the bomb following mole Na]? mixed with the KF. the contents of the bomb used in its Note d-Example 13 was performed using the contents of the bomb following Example 1 and regenerating with GlFg.

Note eExample 23 was periorme completion of Example 22 without regeneration with CiFg.

The chemical action or speed of chemical change involved in the reactions of the process of this invention is affected, as is usual for chemical reactions, by the factor of temperature at which the reactions are run. The above examples show generally that an increase in temperature of the reactants results in an increase in the yield of ClF Performing the reactions of this invention at a temperature or at temperatures in the range of from room temperature to about 80 C. is impractical from a commercial standpoint because the yields are low. For an upper limit of temperature as a factor affecting the process of this invention, the temperature of about 300 C. is selected because above that temperature severe corrosion of the containers results.

With respect to the matter of concentrations of the reactants, inert gasses, e.g., nitrogen and helium, may be present in the reaction zone without affecting the qualitative aspects of the reactions of this invention. Obviously such contaminants Which through combination with fluorine form corrosive products should be avoided. When it is desired to obtain the pure ClF purity of the two reactants avoids the need for separating the desired product from contaminants.

The tetrafiuorochlorates are solids while the other reactant, fluorine, is a gas, and through the reaction between them resulting in the formation of C11 occurs immediately upon bringing the reactants together, the fact that one of the reactants is in the solid phase makes it desirable from a practical standpoint that the tetrafluorochlorates be agitated throughout the time allowed for the reaction to run.

It is apparent from the above examples that changes in pressure are without eifect on the reactions of this invention except insofar as pressure determines eifective concentration of the fluorine gas. In the above examples 150 p.s.i. was the minimum pressure utilized, but such mini d by fiuorinating the contents of the bomb following mum pressure was prescribed only because of the size of the apparatus employed, making it necessary that the fluorine be under pressure in order to provide a sufficient number of fluorine atoms for measurable reactions to occur.

It will be understood that it is intended to cover all changes and modifications of the examples of the invention herein chosen for the purposes of this disclosure, which do not constitute departures from the spirit and scope of the invention.

Having described the invention, what is claimed is:

1. A process for preparing chlorine pentafluoride comprising the steps of reacting fluorine with at least one tetrafluorochlorate of an alkali metal of the group consisting of potassium, cesium and rubidium, and collecting chlorine pentafluoride.

2. The process of claim 1 in which the reaction is run at a temperature in the range of from to 300 C.

3. The process of claim 2 in which the reaction is run at a pressure of at least p.s.i.

4. A proces for preparing chlorine pentafluoride comprising the steps of reacting at least one fluoride of the group consisting of potassium, cesium and rubidium fluoride with chlorine trifluoride, and thereafter subjecting the products of said reaction to reaction with gaseous fluorine, and collecting the chlorine pentafiuoride evolved.

References Cited Science, vol. 141, No. 3585 (Sept. 13, 1963), pp. 1039 and 1040.

MILTON WEISSMAN, Primary Examiner.

OSCAR R. VERTIZ, L. DEWAYNE RUTLEDGE,

Examiners.

G. T. OZAKI, S. TRAUB, Assistant Examiners. 

1. A PROCESS FOR PREPARING CHLORINE PENETAFLUORIDE COMPRISING THE STEPS OF REACTING FLUORIDE WITH AT LEAST ONE ETRAFLUORCHLORATE OF AN ALKLAI METAL OF THE GROUP CONSISTING OF POTASSIUM, CESIUM AND RUBIDUM, AND COLLECTING CHLORINE PENTAFLUORIDE. 